One problem with the tiles disclosed in the patent applications mentioned above is the fact that they may become slippery when wet. In particular when the tiles are made from injection moulded plastics, rubberizes soles, wheels and the like may have difficulties in gaining traction on these surfaces during wet periods and also when a layer of ice has been formed on the surface.
From DE 2213282 is known a construction wherein an element comprising a plurality of upwards facing dimples arranged on a base member, and where further apertures are arranged in between the dimples in the base member. The apertures are arranged such that the element may be lowered over a surface comprising a number of upstanding protrusions. In this manner the dimples increases the effective surface as they will be present in between the protrusions. At the same time the dimples are dimensioned such that they do not protrude above the original surface. With this construction is achieved that the effective surface area is increased, and the possibility of achieving friction between objects and the surface is thereby also increased. A drawback with this construction, however, is that it is not suitable for outdoor use under conditions where rain, sleet, snow and ice may be present. Under such conditions the surface will “fill up” and due to the space provided between the upstanding protrusions and the dimples, the rain, sleet, snow and ice will be trapped in the construction, thereby rendering the surface without the desired friction.